Extruded synthetic foam is generally prepared by melting a base polymeric composition and incorporating one or more blowing agents and optional additives into the polymeric melt under conditions that provide for the thorough mixing of the blowing agent and the polymer while preventing the mixture from foaming prematurely, e.g., under pressure. This mixture may then be extruded through a single or multi-stage extrusion die to cool and reduce the pressure on the mixture, allowing the mixture to foam and produce a foamed product.
Polystyrene is often used to produce foams, since polystyrene foams are good thermal insulators. Polystyrene foams are traditionally less thermally stable at high temperatures than other foamed polymers, which limit the use of polystyrene foams in certain markets.
U.S. 2007/0149711 ('771) discloses a polymeric composition that includes thermally reversible cross-linked bonds. The thermally reversible cross-links are formed by mixing a free-radical reactive polymer, such as polyethylene; a free-radical inducing species; a free radical trapping species; and a complementary thermall-reversible bond contributor. The polymer is capable of forming free radicals when induced by the free radical inducing species.